This is a new project that is aimed at defining insulin resistance to the aging process with the long term goals of developing therapeutic interventions. Synthetic peptides have been made based on the sequence of the insulin receptor beta-subunit in an attempt to prepare an affinity matrix suitable for the purification and characterization of tyrosine protein phosphatase activity that has high specificity toward the insulin receptor. The significance of the project lies in the identification of such insulin receptor-specific phosphatase(s) in intact cell, as well as in the characterization of insulin resistance secondary to variation phosphatase activity.